The invention relates to a teatcup assembly for milking a mammal, and more particularly to a teatcup liner with a clog resistant air vent plug.
Teatcup assemblies having a liner with an air vent plug are known in the prior art, for example U.S. Pat. Nos. 3,476,085, 3,659,558, 3,967,586, 3,967,587, 4,303,038, all incorporated herein by reference. A plurality of teatcups are connected to respective teats depending from the udder of a mammal such as a cow. Each teatcup assembly has a teatcup liner or inflation around a respective teat and defining a milk flow passage within the liner below the teat, and a pulsation chamber outside the liner between the liner and the teatcup shell, all as known in the prior art, for example U.S. Pat. Nos. 4,269,143, 4,530,307, 5,178,095, 5,218,924, all incorporated herein by reference. The system has a milking cycle with an on portion and an off portion. Milk flows from the teat towards a milking claw during the on portion, and then to a storage vessel. During the off portion, the liner is collapsed around the teat, to aid in the circulation of body fluids. Vacuum is continuously applied to the milk flow passage within the liner. Vacuum is alternately and cyclically applied to the pulsation chamber between the liner and the teatcup shell, to open and close the liner, all as is known.
The air vent plug has a calibrated vent or air port therein open to atmospheric pressure for admitting air to the upper end of the milk tube portion of the liner below the teatcup shell. As the liner opens during the milking phase on portion of the cycle, milk flows from the teat into the liner. During the off portion of the cycle, the liner is collapsed and closed. During the on portion of the cycle, the liner is open. The opening movement of the liner causes a reduction in the pressure within the liner, and the milk remaining in the liner from the previous cycle will suck backwards or be forced upwardly into the reduced pressure area around the teat end. This backwash of milk is undesirable. The noted air vent plug solves this problem by admitting a calibrated amount of air into the liner to enable the milk to be rapidly carried away from the teat end, and prevent the liner from acting like a suction pump.
The present invention provides an improved air vent plug. In one particularly desirable aspect, the invention overcomes clogging problems in prior air vent plugs, while retaining cost efficient manufacturability.